This is interesting -- I'm glad to see it quantified.
http://web.mit.edu/newsoffice/2012/p...ires-0523.html
It is obvious at intersections where vehicles tend to sit still in line waiting for the traffic signal light to change -- the wheel ruts are quite pronounced on many roads around here. I tend to drive slightly to the right of the the ruts and ripples to avoid the roughness.
We need to build better road foundations. This would make roads last a (lot) longer with less maintenance; as well as save fuel.